One of the most important steps in the manufacture of high quality printing papers, coated or uncoated, is the calendering of the paper web to impart gloss and smoothness to its surface. A number of different processes exist for calendering paper. One long used for producing the highest quality product is supercalendering. Gloss calendering is another process, which while not producing the quality of supercalendering, does have process advantages over supercalendering. Substrata thermal molding is a recently developed calendering process which combines process advantages of gloss calendering with the quality advantages of supercalendering. Substrata thermal molding is described in U.S. Pat. Nos. 4,624,744 and 4,749,445, which patents are hereby incorporated by reference.
In both gloss calendering and substrata thermal molding the outer surface of the heated calender roll must have a hard highly polished surface. The roll drum is traditionally made from chilled iron, ductile iron or chrome plated ductile iron, which provides a hard, abrasion resistant surface which takes and holds a high polish. More recently developed heated rolls include metal rolls coated with a thin layer of very hard materials, such as carbide containing materials. These recently employed surface materials deteriorate when faced with abrasive paper coating materials, the abrasive action of a cleaning doctor blade, and a corrosive environment. They must be resurfaced periodically and it would be preferably to do so while in operation.